1. Field of the Invention
The present invention relates to an exhaust manifold for an exhaust line of an internal combustion engine, of the type comprising:                an outer casing comprising:        an outer shell;        a flange which is welded to the outer shell and which has a surface for abutment against an engine cylinder head and at least one aperture which opens at the abutment surface,        at least one inner channel which is arranged in the outer casing and which opens via an aperture.        
2. Description of the Related Art
Currently, vehicles having heat engines are provided with exhaust lines which include depollution elements such as catalytic purification elements and/or particulate filters. In order to allow these depollution elements to operate in a satisfactory manner, the exhaust gases must reach them at a high temperature. It is therefore advantageous to prevent an excessive loss of heat in the exhaust line and in particular in the manifold which separates the outlet of the heat engine from the first depollution element.
Various solutions have been envisaged for this purpose. In particular, manifolds which comprise inner channels which are retained in an external shell which is separated from the inner channels by an air space or an insulating material are found to be effective in preventing an excessive loss of heat.
These manifolds comprise a flange for fixing to the engine cylinder head on which the inner channels, on the one hand, and the outer shell, on the other hand are supported.
It has been found that the metal flange dissipates a large amount of thermal energy from the exhaust gases as they pass through the flange.